1. Field of the Invention
The present invention relates generally to compositions and methods for treating loosely consolidated and/or unconsolidated subterranean formations. In another aspect, the present invention relates to consolidating loosely consolidated and/or unconsolidated subterranean formations proximate a wellbore while maintaining at least part of the permeability of the formation.
2. Description of the Prior Art
Oil and gas producing wells are often completed in loosely consolidated and/or unconsolidated subterranean production formations which often cause sand or other incompetent formation material to flow into a wellbore along with production fluids. The production of such sand or incompetent formation material along with production fluids tends to cause erosion and/or plugging of production equipment, substantially increasing the costs of well operation.
The use of gravel packs is a known method in the art for preventing the migration of incompetent formation material into a wellbore during the production of fluids from a subterranean formation. In gravel packing operations, a pack of gravel is typically placed in the annulus between a perforated or slotted casing or screen and the walls of the wellbore in the producing interval. The resulting structure provides a barrier to migrating sand or incompetent formation material from the producing formation while allowing the flow of production fluids into the wellbore. However, while gravel packs successfully prevent the production of incompetent formation material with formation fluids, they often fail and require replacement, due to, for example, the deterioration of the casing or screen as a result of corrosion, plugging, and the like. The initial placement of gravel packs adds considerable costs to the completion of a well, and replacement of such gravel packs after completion is even more costly.
Another method of preventing the migration of incompetent formation material known in the art is the use of cement to consolidate, or at least partially consolidate, sand or other incompetent formation material in a subterranean production formation proximate the wellbore. One of the concerns in using such a method is maintaining the permeability of the formation proximate the wellbore, so as to allow the continued production of formation fluids, while at the same time preventing the migration of sand or incompetent formation material into the wellbore. To meet this concern, one type of method involves the use of foamed cements, whereby a foamed cement composition is produced at surface level. Such a composition usually comprises cement, water, and a gas, typically nitrogen or air. The foamed cement is usually then sent down the wellbore and allowed to set near the production formation.
However, there still remains a need for improved methods and compositions for consolidating, or at least partially consolidating, unconsolidated production formations to prevent the migration of sand and other incompetent formation material along with production fluids from a production formation while at the same time maintaining permeability in the production zone.